Method of processing target object

ABSTRACT

A method of processing a target object is provided. The target object includes a first protrusion portion, a second protrusion portion, an etching target layer and a groove portion. The groove portion is provided on a main surface of the target object, provided on the etching target layer and defined by the first and the second protrusion portions. An inner surface of the groove portion is included in the main surface. In the method, a first sequence is repeatedly performed N times (N is an integer equal to or larger than 2). The first sequence includes (a) forming a protection film conformally on the main surface in a processing vessel of a plasma processing apparatus in which the target object is accommodated; and (b) etching a bottom portion of the groove portion with plasma of a gas generated within the processing vessel after the process a is performed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2016-167071 filed on Aug. 29, 2016, the entire disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to a method ofprocessing a target object; and, more particularly, to a method ofperforming a surface processing on a semiconductor substrate withplasma.

BACKGROUND

A plasma processing may be performed on a target object such as a waferby using a plasma processing apparatus. A plasma etching is one kind ofsuch a plasma processing. The plasma etching is performed to transcribea pattern of a mask formed on an etching target layer to the etchingtarget layer. Generally, the mask is implemented by a resist mask. Theresist mask is formed by a photolithography technique. Thus, a limitsize of the pattern formed on the etching target layer depends on aresolution of the resist mask formed by the photolithography technique.

As a demand for high integration of electronic devices is gettinghigher, it is required to form the pattern smaller than the resolutionlimit of the resist mask. However, there is a limit in the resolution ofthe resist mask. Thus, as described in Patent Document 1, there isproposed a technique of adjusting a size of the resist mask and reducinga width of an opening provided in the resist mask by forming a siliconoxide film on the resist mask.

-   Patent Document 1: Japanese Patent Laid-open Publication No.    2004-080033

Meanwhile, as the electronic devices are miniaturized to meet the recenttrend of the high integration, it is required to control a criticaldimension (CD) with high accuracy when forming the pattern on the targetobject. Further, it may also be required to form various shapes ofpatterns.

As stated above, with regard to the pattern formation on the targetobject, it is required to develop a technique capable of coping withformation of various shapes of patterns as well as miniaturization ofthe patterns to meet the recent trend of high integration.

SUMMARY

In an exemplary embodiment, there is provided a method of processing atarget object. The target object includes a first protrusion portion, asecond protrusion portion, an etching target layer and a groove portion.The etching target layer has a region belonging to the first protrusionportion and a region belonging to the second protrusion portion. Thegroove portion is provided on a main surface of the target object,provided on the etching target layer and defined by the first protrusionportion and the second protrusion portion. An inner surface of thegroove portion is included in the main surface of the target object. Inthe method, a first sequence is repeatedly performed N times (N is aninteger equal to or larger than 2). The first sequence includes forminga protection film conformally on the main surface of the target objectin a processing vessel of a plasma processing apparatus in which thetarget object is accommodated (referred to as “process a”); and etchinga bottom portion of the groove portion of the target object with plasmaof a gas generated within the processing vessel after the process a isperformed (referred to as “process b”).

In the method, the process a of conformally forming the protection filmon the main surface of the target object (including the inner surface ofthe groove portion) and the process b of etching the bottom portion ofthe groove portion provided on the main surface after the process a maybe alternately repeated. Thus, by appropriately adjusting the filmthickness of the protection film or the like for each of the multiplecycles of the process a and by appropriately adjusting the etchingamount or the like for each of the multiple cycles of the process b, thegroove portion can be processed with relatively high accuracy accordingto the various required shapes of the groove portion.

In the process a, the protection film may be conformally formed on themain surface of the target object by repeatedly performing a secondsequence including supplying a first gas into the processing vessel(referred to as “process c”); purging a space within the processingvessel after the process c is performed (referred to as “process d”);generating plasma of a second gas within the processing vessel after theprocess d is performed (referred to as “process e”); and purging thespace within the processing vessel after the process e is performed. Inthe process c, plasma of the first gas may not be generated. As statedabove, in the process a, since the protection film is conformally formedon the main surface of the target object (including the inner surface ofthe groove portion) by the same method as the ALD (Atomic LayerDeposition) method, the strength of protection of the main surface ofthe target object can be improved, and the protection film forprotecting the main surface of the target object can be formed in theuniform thickness.

In the process a, the protection film may be conformally formed on themain surface of the target object by supplying a first gas into theprocessing vessel (referred to as “process f”) and purging a spacewithin the processing vessel after the process f is performed. In theprocess b following the process a, the bottom portion of the grooveportion of the target object may be etched with plasma of anoxygen-containing gas generated within the processing vessel. In theprocess f, plasma of the first gas may be not generated. As statedabove, since the process a only consists of the process f of forming thereaction precursor on the main surface of the target object (includingthe inner surface of the groove portion) with the first gas and theprocess of purging the space within the processing vessel after theprocess f is performed, the protection film formed through the process acan be formed of the reaction precursor formed through the process f,and, accordingly, can be a relatively thin film. In addition, since theplasma of the oxygen-containing gas is used in the process b followingthe process a, oxygen can be added to the reaction precursor formed inthe process f, and the protection film having the same composition asthe protection film formed by the same method as the ALD method can beformed to have a relatively thin thickness. Furthermore, since theaddition of the oxygen gas can be performed during the etching of theprocess b, high efficiency of the processing can be achieved.

In the performing of the first sequence repeatedly N times, the firstsequence including a first processing may be performed M times (M is aninteger equal to or lager than 1 and equal to or smaller than N−1), andthe first sequence including a second processing may be performed N−Mtimes. The first processing may be included in the process a. In thefirst processing, the protection film may be conformally formed on themain surface of the target object by repeatedly performing a secondsequence including supplying a first gas into the processing vessel(referred to as “process g”); purging a space within the processingvessel after the process g is performed (referred to as “process h”);generating plasma of a second gas within the processing vessel after theprocess h is performed (referred to as “process i”); and purging thespace within the processing vessel after the process i is performed. Thesecond processing may be included in the process a. In the secondprocessing, the protection film may be conformally formed on the mainsurface of the target object by supplying the first gas into theprocessing vessel (referred to as “process j”) and purging the spacewithin the processing vessel after the process j is performed. In theprocess b following the second processing, the bottom portion of thegroove portion of the target object may be etched by plasma of anoxygen-containing gas generated within the processing vessel. Plasma ofthe first gas may not be generated in the process g performed in thefirst processing and the process j performed in the second processing.As stated above, in the first processing, since the protection film isconformally formed on the main surface of the target object (includingthe inner surface of the groove portion) by the same method as the ALDmethod, the strength of the protection of the main surface of the targetobject can be improved, and the protection film for protecting the mainsurface of the target object can be formed in the uniform thickness.Further, since the second processing only consists of the process j offorming the reaction precursor on the main surface of the target object(including the inner surface of the groove portion) with the first gasand the process of purging the space within the processing vessel afterthe process j is performed, the protection film formed through thesecond processing can be formed of the reaction precursor formed throughthe process j, and, accordingly, can become a relatively thin film. Inaddition, since the plasma of the oxygen-containing gas is used in theprocess b following the second processing, oxygen can be added to thereaction precursor formed in the process j, and the protection filmhaving the same composition as the protection film formed by the samemethod as the ALD method can be formed to have a relatively thinthickness. Furthermore, since the addition of the oxygen gas can beperformed during the etching of the process b, high efficiency of theprocessing can be achieved. Further, in performing the N cycles of thefirst sequence, since the first sequence including the aforementionedfirst processing is performed M times and the first sequence includingthe aforementioned second processing is performed N−M times, it ispossible to cope with the formation of various shapes of the grooveportion sufficiently.

The second gas may contain oxygen atoms. By way of example, the secondgas may contain a carbon dioxide gas or an oxygen gas. As stated above,since the second gas contains the oxygen atoms, in each of the process eand the process i, the reaction precursor of the silicon formed in eachof the process c and the process g is bond with the oxygen atoms, sothat the protection film of the silicon oxide can be conformally formed.Moreover, in case that the second gas is the carbon dioxide gas, sincethe second gas contains the carbon atoms, damage caused by the oxygenatoms can be suppressed by the carbon atoms.

The first gas may contain an aminosilane-based gas. As stated above,since the first gas contains the aminosilane-based gas, the reactionprecursor of the silicon can be formed along an atomic layer of the mainsurface of the target object through each of the process c, process fand the process g.

The first gas may contain monoaminosilane. As stated above, by using thefirst gas containing the monoaminosilane, the reaction precursor of thesilicon can be formed through each of the process c, process f and theprocess g.

The aminosilane-based gas contained in the first gas may includeaminosilane having one to three silicon atoms. The aminosilane-based gascontained in the first gas may include aminosilane having one to threeamino groups. As stated, the aminosilane having the one to three siliconatoms can be used as the aminosilane-based gas contained in the firstgas. Alternatively, the aminosilane having the one to three amino groupscan be used as the aminosilane-based gas contained in the first gas.

A film thickness of the protection film formed in the process a may beequal to or larger than 2 nm and equal to or smaller than 8 nm beforethe process b is performed. As stated above, before the process b isperformed, if the film thickness of the protection film formed in theprocess a is in the range from 2 nm to 8 nm, the etching effect upon thecorner portion of the target object covered with the protection film canbe reduced, as compared to the case where the film thickness of theprotection film is below 2 nm, particularly. Thus, the degree ofdeformation of the target object caused by the etching of the process bcan be reduced.

According to the exemplary embodiments as described above, in formingthe pattern on the target object, it is possible to provide a techniquecapable of coping with the formation of various shapes of patterns aswell as achieving miniaturization of the patterns to meet a trend ofhigher integration.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described asillustrations only since various changes and modifications will becomeapparent to those skilled in the art from the following detaileddescription. The use of the same reference numbers in different figuresindicates similar or identical items.

FIG. 1A is a flowchart for describing major processes of a methodaccording to an exemplary embodiment;

FIG. 1B is a flowchart for specifically describing a part of theprocesses shown in FIG. 1A; and FIG. 1C is another flowchart forspecifically describing a part of the processes shown in FIG. 1A;

FIG. 2 is a diagram illustrating an example of a plasma processingapparatus;

FIG. 3 is a cross sectional view illustrating a state of a target objectbefore the individual processes shown in FIG. 1A to FIG. 1C areperformed;

FIG. 4A and FIG. 4B are cross sectional views sequentially illustratingstates of the target object after the individual processes shown in FIG.1A to FIG. 1C are performed;

FIG. 5A and FIG. 5B are cross sectional views sequentially illustratingstates of the target object after the individual processes shown in FIG.1A to FIG. 1C are performed;

FIG. 6A to FIG. 6C are diagrams sequentially and schematicallyillustrating formation of a protection film in performing a sequence offorming the protection film shown in FIG. 1A to FIG. 1C; and

FIG. 7 is a diagram showing an example of a measurement result showing acorrespondence between a film thickness of the protection film shown inFIG. 4A and a height of a corner portion of an etching target layerformed by etching shown in FIG. 4B.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the description. In thedrawings, similar symbols typically identify similar components, unlesscontext dictates otherwise. Furthermore, unless otherwise noted, thedescription of each successive drawing may reference features from oneor more of the previous drawings to provide clearer context and a moresubstantive explanation of the current exemplary embodiment. Still, theexemplary embodiments described in the detailed description, drawings,and claims are not meant to be limiting. Other embodiments may beutilized, and other changes may be made, without departing from thespirit or scope of the subject matter presented herein. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein and illustrated in the drawings, may bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

Hereinafter, various exemplary embodiments will be described in detailwith reference to the accompanying drawings. Same or corresponding partsin the various drawings will be assigned same reference numerals.

FIG. 1A to FIG. 1C are flowcharts for describing a method according toan exemplary embodiment. A method MT of the present exemplary embodimentshown in FIG. 1A to FIG. 1C is directed to processing a target object(hereinafter, referred to as “wafer”). The method MT includes, as shownin FIG. 1A, a sequence SQ1 (a first sequence). The sequence SQ1 includesa process ST1 and a process ST2. The method MT further includes aprocess ST3. The process ST1 may include a process ST1 a (a firstprocessing) shown in FIG. 1B. The process ST1 may include a process ST1b (a second processing) shown in FIG. 1C. Further, though the method MTof the present exemplary embodiment can be performed by using a singleplasma processing apparatus (a plasma processing apparatus 10 to bedescribed later), it may be also possible to use a plurality of plasmaprocessing apparatuses 10 for the individual processes of the method MT.

FIG. 2 is a diagram showing an example of a plasma processing apparatus.FIG. 2 schematically illustrates a cross sectional configuration of theplasma processing apparatus 10 which can be used in various exemplaryembodiments of processing a target object. As depicted in FIG. 2, theplasma processing apparatus 10 is configured as a capacitively coupledplasma etching apparatus.

The plasma processing apparatus 10 includes a processing vessel 12, anexhaust opening 12 e, a carry-in/out opening 12 g, a supporting member14, a placing table PD, a DC power supply 22, a switch 23, a coolantpath 24, a pipeline 26 a, a pipeline 26 b, an upper electrode 30, aninsulating shield member 32, an electrode plate 34, a gas dischargeholes 34 a, an electrode supporting body 36, a gas diffusion space 36 a,gas through holes 36 b, a gas inlet opening 36 c, a gas supply line 38,a gas source group 40, a valve group 42, a flow rate controller group45, a deposition shield 46, a gas exhaust plate 48, a gas exhaust device50, a gas exhaust line 52, a gate valve 54, a first high frequency powersupply 62, a second high frequency power supply 64, a matching device66, a matching device 68, a power supply 70, a control unit Cnt, a focusring FR, a heater power supply HP, and a heater HT. The placing table PDis equipped with an electrostatic chuck ESC and a lower electrode LE.The lower electrode LE includes a first plate 18 a and a second plate 18b. The processing vessel 12 forms a processing space Sp therein.

The processing vessel 12 has a substantially cylindrical shape. Theprocessing vessel 12 is made of, for example, aluminum. An inner wallsurface of the processing vessel 12 is anodically oxidized. Theprocessing vessel 12 is frame-grounded.

The supporting member 14 is provided on a bottom portion of theprocessing vessel 12 inside the processing vessel 12. The supportingmember 14 has a substantially cylindrical shape. The supporting member14 is made of, by way of example, an insulating material. The insulatingmaterial forming the supporting member 14 may contain oxygen, forexample, quartz. Within the processing vessel 12, the supporting member14 is vertically extended from the bottom portion of the processingvessel 12.

The placing table PD is provided within the processing vessel 12. Theplacing table PD is supported by the supporting member 14. The placingtable PD holds a wafer W on a top surface thereof. The wafer W is thetarget object. The placing table PD is equipped with the lower electrodeLE and the electrostatic chuck ESC.

The lower electrode LE includes the first plate 18 a and the secondplate 18 b. The first plate 18 a and the second plate 18 b are made of ametal such as, but not limited to, aluminum. The first plate 18 a andthe second plate 18 b have a substantially disc shape. The second plate18 b is provided on the first plate 18 a and electrically connected tothe first plate 18 a.

The electrostatic chuck ESC is provided on the second plate 18 b. Theelectrostatic chuck ESC has a pair of insulating layers or insulatingsheets; and an electrode, which serves as a conductive film, embeddedtherebetween. The electrode of the electrostatic chuck ESC iselectrically connected to the DC power supply 22 via the switch 23. Theelectrostatic chuck ESC attracts the wafer W by an electrostatic forcesuch as a Coulomb force generated by a DC voltage applied from the DCpower supply 22. With this configuration, the electrostatic chuck ESC iscapable of holding the wafer W.

The focus ring FR is placed on a peripheral portion of the second plate18 b to surround an edge of the wafer W and the electrostatic chuck ESC.The focus ring FR is configured to improve etching uniformity. The focusring FR is made of a material which is appropriately selected dependingon a material of an etching target film. By way of example, the focusring FR may be formed of quartz.

The coolant path 24 is provided within the second plate 18 b. Thecoolant path 24 constitutes a temperature controller. A coolant issupplied into the coolant path 24 from a chiller unit provided outsidethe processing vessel 12 via the pipeline 26 a. The coolant suppliedinto the coolant path 24 is then returned back into the chiller unit viathe pipeline 26 b. In this way, the coolant is supplied into the coolantpath 24 to be circulated therein. A temperature of the wafer W held bythe electrostatic chuck ESC is controlled by adjusting a temperature ofthe coolant. Through the gas supply line 28, a heat transfer gas, e.g.,a He gas, is supplied from a heat transfer gas supply device into a gapbetween a top surface of the electrostatic chuck ESC and a rear surfaceof the wafer W.

The heater HT is a heating device. By way of non-limiting example, theheater HT is buried in the second plate 18 b. The heater HT is connectedto a heater power supply HP. As a power is supplied to the heater HTfrom the heater power supply HP, a temperature of the placing table PDis adjusted, so that a temperature of the wafer W placed on the placingtable PD is adjusted. Further, the heater HT may be embedded in theelectrostatic chuck ESC.

The upper electrode 30 is provided above the placing table PD, facingthe placing table PD. The lower electrode LE and the upper electrode 30are arranged to be substantially parallel to each other. Providedbetween the upper electrode 30 and the lower electrode LE is theprocessing space Sp in which a plasma processing is performed on thewafer W.

The upper electrode 30 is supported at an upper portion of theprocessing vessel 12 with the insulating shield member 32 therebetween.The insulating shield member 32 is made of an insulating material andmay contain oxygen for example, but not limited to, quartz. The upperelectrode 30 may include the electrode plate 34 and the electrodesupporting body 36. The electrode plate 34 faces the processing spaceSp, and is provided with a multiple number of gas discharge holes 34 a.In the exemplary embodiment, the electrode plate 34 may be made ofsilicon. In another exemplary embodiment, the electrode plate 34 may bemade of silicon oxide.

The electrode supporting body 36 is configured to support the electrodeplate 34 in a detachable manner, and is made of a conductive materialsuch as, but not limited to, aluminum. The electrode supporting body 36may have a water-cooling structure. The gas diffusion space 36 a isformed within the electrode supporting body 36. The multiple gas throughholes 36 b are extended downwards (towards the placing table PD) fromthe gas diffusion space 36 a, and these gas through holes 36 brespectively communicate with the gas discharge holes 34 a.

Through the gas inlet opening 36 c, a processing gas is introduced intothe gas diffusion space 36 a. This gas inlet opening 36 c is provided atthe electrode supporting body 36 and connected with the gas supply line38.

The gas source group 40 is connected to the gas supply line 38 via thevalve group 42 and the flow rate controller group 45. The gas sourcegroup 40 includes a plurality of gas sources. These gas sources mayinclude a source of an aminosilane-based gas, a source of a fluorocarbongas (hydrofluorocarbon gas), a source of an oxygen (O₂) gas, a source ofan inert gas, a source of a rare gas and a source of a carbon dioxidegas. As the aminosilane-based gas (which is contained in the first gasG1 to be described later), one having a molecular structure with arelatively small number of amino groups may be used. By way ofnon-limiting example, monoaminosilane (H₃—Si—R (R denotes an amino groupwhich contains an organic group and may be substituted)) may be used.The aforementioned aminosilane-based gas (which is contained in thefirst gas G1 to be described later) may include aminosilane having oneto three silicon atoms and aminosilane having one to three amino groups.The aminosilane having the one to three silicon atoms may be monosilane(monoaminosilane) having one to three amino groups, disilane having oneto three amino groups, or trisilane having one to three amino groups.Further, the aforementioned aminosilane may have an amino group whichmay be substituted. The amino group may be substituted with any one of amethyl group, an ethyl group, a propyl group or a butyl group.Furthermore, the aforementioned methyl group, the ethyl group, thepropyl group or the butyl group may be substituted with a halogen. Thefluorocarbon gas may be implemented by, by way of example, but notlimitation, a CF₄ gas, a C₄F₆ gas, a C₄F₈ gas, or the like. The inertgas may be implemented by, for example, a nitrogen (N₂) gas or the like.The rare gas may be implemented by, for example, an Ar gas, or the like.

The valve group 42 includes a multiple number of valves, and the flowrate controller group 45 includes a multiple number of flow ratecontrollers such as mass flow controllers. Each of the gas sourcesbelonging to the gas source group 40 is connected to the gas supply line38 via each corresponding valve belonging to the valve group 42 and eachcorresponding flow rate controller belonging to the flow rate controllergroup 45. Accordingly, in the plasma processing apparatus 10, it ispossible to supply a gas from one or more gas sources selected from theplurality of gas sources belonging to the gas source group 40 into theprocessing vessel 12 at individually controlled flow rate(s). Further,in the plasma processing apparatus 10, a deposition shield 46 isprovided along an inner wall of the processing vessel 12 in a detachablemanner. The deposition shield 46 is also provided on an outer sidesurface of the supporting member 14. The deposition shield 46 isconfigured to suppress an etching byproduct (deposit) from adhering tothe processing vessel 12, and is formed by coating an aluminum memberwith Y₂O₃ or the like. Besides the Y₂O₃, the deposition shield may bemade of an oxygen-containing material such as, but not limited to,quartz.

At a bottom side of the processing vessel 12, the gas exhaust plate 48is provided between the supporting member 14 and a side wall of theprocessing vessel 12. The gas exhaust plate 48 may be made of, by way ofexample, an aluminum member coated with ceramic such as Y₂O₃ or thelike. The gas exhaust opening 12 e is provided in the processing vessel12 under the gas exhaust plate 48. The gas exhaust opening 12 e isconnected with the gas exhaust device 50 via the gas exhaust line 52.The gas exhaust device 50 includes a vacuum pump such as a turbomolecular pump, and is capable of decompressing the space within theprocessing vessel 12 to a required vacuum level. Through thecarry-in/out opening 12 g, the wafer W is carried into or out of theprocessing vessel 12. The carry-in/out opening 12 g is provided at theside wall of the processing vessel 12, and the carry-in/out opening 12 gis opened or closed by the gate valve 54.

The first high frequency power supply 62 is configured to generate afirst high frequency power for plasma generation, for example, a highfrequency power of 40 MHz having a frequency ranging from 27 MHz to 100MHz. The first high frequency power supply 62 is connected to the upperelectrode 30 via the matching device 66. The matching device 66 is acircuit configured to match an output impedance of the first highfrequency power supply 62 and an input impedance at a load side (lowerelectrode LE side). The first high frequency power supply 62 may beconnected to the lower electrode LE via the matching device 66.

The second high frequency power supply 64 is configured to generate asecond high frequency power for attracting ion into the wafer W, thatis, a high frequency bias power. By way of example, the second highfrequency power supply 64 generates a high frequency bias power of 3.2MHz having a frequency ranging from 400 kHz to 40.68 MHz. The secondhigh frequency power supply 64 is connected to the lower electrode LEvia a matching device 68. The matching device 68 is a circuit configuredto match an output impedance of the second high frequency power supply64 and the input impedance at the load side (lower electrode LE side).Further, the power supply 70 is connected to the upper electrode 30. Thepower supply 70 is configured to apply, to the upper electrode 30, avoltage for attracting positive ions within the processing space Sp intothe electrode plate 34. As an example, the power supply 70 is a DC powersupply configured to generate a negative DC Voltage. If such a voltageis applied to the upper electrode 30 from the power supply 70, thepositive ions existing within the processing space Sp collide with theelectrode plate 34. As a result, secondary electrons and/or silicon isreleased from the electrode plate 34.

The control unit Cnt is implemented by a computer including a processor,a storage unit, an input device, a display device, and so forth, and isconfigured to control individual components of the plasma processingapparatus 10. To elaborate, the control unit Cnt is connected to thevalve group 42, the flow rate controller group 45, the gas exhaustdevice 50, the first high frequency power supply 62, the matching device66, the second high frequency power supply 64, the matching device 68,the power supply 70, the heater power supply HP and the chiller unit.

The control unit Cnt is operated to output control signals according toa program based on an input recipe. The selection of the gas suppliedfrom the gas source group and a flow rate of the selected gas, the gasexhaust of the gas exhaust device 50, power supplies from the first andsecond high frequency power supplies 62 and 64, application of thevoltage from the power supply 70, the power supply of the heater powersupply HP, the control of the flow rate and the temperature of thecoolant from the chiller unit can be achieved in response to the controlsignals from the control unit Cnt. Further, individual processes of themethod MT (shown in FIG. 1) of processing a target object according tothe present exemplary embodiment can be performed as the individualcomponents of the plasma processing apparatus 10 are operated under thecontrol of the control unit Cnt.

Now, referring back to FIG. 1A to FIG. 1C, the method MT will bediscussed in detail. In the following, an example where the plasmaprocessing apparatus 10 is used to perform the method MT will beexplained. The following description refers to FIG. 3 to FIG. 7 as wellas FIG. 1A to FIG. 1C and FIG. 2. FIG. 3 is a cross sectional viewillustrating a state of a target object before individual processesshown in FIG. 1A to FIG. 1C are performed. FIG. 4A and FIG. 4B are crosssectional views sequentially illustrating states of the target objectafter the individual processes shown in FIG. 1A to FIG. 1C areperformed. FIG. 5A and FIG. 5B are cross sectional views sequentiallyillustrating states of the target object after the individual processesshown in FIG. 1A to FIG. 1C are performed. FIG. 6A to FIG. 6C areschematic diagrams sequentially illustrating formation of a protectionfilm in performing a sequence of forming the protection film shown inFIG. 1A to FIG. 1C.

Prior to performing the method MT shown in FIG. 1A to FIG. 1C, a wafer Wshown in FIG. 3 is carried into the processing vessel 12. The wafer Willustrated in FIG. 3 is an example of the target object to which themethod MT of FIG. 1A to FIG. 1C is applied. The wafer W shown in FIG. 3is a substrate product formed through a dual damascene etching process.The wafer W shown in FIG. 3 has a protrusion portion CV1 (firstprotrusion portion), a protrusion portion CV2 (second protrusionportion), an etching target layer PM and a groove portion TR. Theetching target layer PM includes a region PM1 belonging to theprotrusion portion CV1 and a region PM2 belonging to the protrusionportion CV2. The groove portion TR is provided on a main surface SC ofthe wafer W. The groove portion TR is provided at the etching targetlayer PM. The groove portion TR is defined by the protrusion portion CV1and the protrusion portion CV2.

The wafer W depicted in FIG. 3 further includes a mask MK and adeposition film DP. The mask MK is provided on the region PM1.Specifically, the mask MK is provided on an end surface SF1 of theregion PM1 (that is, an interface between the region PM1 and the maskMK). The deposition film DP is provided on the mask MK.

An inner surface SF2 of the groove portion TR includes a surface SF2 a,a surface SF2 b and a surface SF2 c. The etching target layer PMincludes the end surface SF1 and the surface SF2 a at the protrusionportion CV1. The surface SF2 a is a part of the surface SF2 at the sideof the protrusion portion CV1. The surface SF2 b is located at a bottomportion BT of the groove portion TR. That is, the surface SF2 b is abottom surface of the groove portion TR. The surface SF2 c is a part ofthe surface SF2 at the side of the protrusion portion CV2 and faces thesurface SF2 a. The etching target layer PM includes the surface SF2 cand an end surface SF3 at the protrusion portion CV2. The end surfaceSF1, the surface SF2 and the end surface SF3 belong to the main surfaceSC of the wafer W.

A width LP1 of the groove portion TR is a distance between the surfaceSF2 a and the surface SF2 c and is, for example, 3 nm to 5 nm. A heightdifference LP2 is a distance between the end surface SF1 and the endsurface SF3. A plane including the end surface SF1 is located above theend surface SF3. In this case, the height difference LP2 has a positivevalue. By performing the method MT, the region PM2 of the etching targetlayer PM at the protrusion portion CV2 is etched from a side of the endsurface SF3, so that the height difference LP2 is increased.

The etching target layer PM is a porous film provided with a multiplenumber of holes. The etching target layer PM has a low dielectricconstant (low-k). The etching target layer PM may be made of, by way ofnon-limiting example, SiOCH. The mask MK may be made of, by way ofexample, but not limitation, TiN. The deposition film DP may be made of,for example, CF.

Referring back to FIG. 1A to FIG. 1C, in the method MT, a sequence SQ1is performed one or more times. A series of processes from the start ofthe sequence SQ1 to a process ST3 (process ST3: YES) to be describedlater is an etching process for obtaining a required shape of the grooveportion TR of the etching target layer PM. After the wafer W shown inFIG. 3 is carried in, the sequence SQ1 is performed. In the method MT,the sequence SQ1 is repeatedly performed N times (N is an integer equalto or lager than 2). The sequence SQ1 includes a process ST1 and aprocess ST2. The process ST1 is performed to form a protection film SXconformally on the main surface SC of the wafer W within the processingvessel 12 of the plasma processing apparatus 10 in which the wafer W isaccommodated. An example of the process ST1 is a process ST1 a shown inFIG. 1B. Another example of the process ST1 is a process ST1 b shown inFIG. 1C.

The process ST1 a includes a sequence SQ1 a (second sequence). Thesequence SQ1 a includes a process ST11 a, a process ST12 a, a processST13 a and a process ST14 a.

Between the process ST1 a and the process ST1 b, the process ST1 a willbe first explained with reference to FIG. 1B. The process ST1 a includesthe sequence SQ1 a. The sequence SQ1 a includes the process ST11 a, theprocess ST12 a, the process ST13 a and the process ST14 a. The processST1 a further includes a process ST15 a.

In the process ST1 a, the sequence SQ1 a is performed one or more times.A series of processes from the start of the sequence SQ1 a to theprocess ST15 a (process ST15 a: YES) to be described later is a processof forming the protection film SX conformally on the main surface SC(particularly, the surface SF2 a, the surface SF2 b, the surface SF2 cand the end surface SF3) of the wafer W.

First, in the process ST11 a, the first gas G1 containing silicon issupplied into the processing vessel 12. The first gas G1 contains anaminosilane-based gas. The first gas G1 is supplied into the processingvessel 12 from a gas source selected from the plurality of gas sourcesbelonging to the gas source group 40. The first gas G1 is anaminosilane-based gas such as, but not limited to, monoaminosilane(H₃—Si—R (R denotes an amino group)). In the process ST11 a, plasma ofthe first gas G1 is not generated.

As shown in FIG. 6A, molecules of the first gas G1 adhere to the mainsurface SC of the wafer W as reaction precursors. The molecules(monoaminosilane) of the first gas G1 adhere to the main surface SC ofthe wafer W by chemical adsorption based on chemical bonding, and plasmais not used in the process ST11 a. Further, a gas other than themonoaminosilane may be used as long as the gas contains silicon and canbe attached to the surface of the wafer W by the chemical bonding.

The monoaminosilane-based gas is selected as the first gas G1 becausethe chemical adsorption of the monoaminosilane can take place relativelyeasily since it has relatively high electronegativity and a molecularstructure with polarity. A layer Ly1 formed as the molecules of thefirst gas G1 adhere to the main surface SC of the wafer W comes into astate close to a monomolecular layer (monolayer) since the adhesion isachieved by the chemical adsorption. Here, the smaller the amino group Rof the monoaminosilane is, the smaller the molecular structure of themolecules adsorbed to the main surface SC of the wafer W may be and,thus, steric hindrance which depends on the size of the molecules may bereduced. Therefore, the molecules of the first gas G1 can be uniformlyadsorbed to the main surface SC of the wafer W, so that the layer Ly1can be formed to have a uniform film thickness on the main surface SC ofthe wafer W. By way of example, as the monoaminosilane (H₃—Si—R)contained in the first gas G1 reacts with OH groups on the main surfaceSC of the wafer W, H₃—Si—O as the reaction precursors are formed, sothat the layer Ly1 formed of the monolayer of H₃—Si—O is obtained. Thus,the layer L1 y of the reaction precursor is formed on the main surfaceSC of the wafer W conformally to have a uniform film thickness withoutbeing affected by a pattern density of the wafer W.

In the process ST12 a following the process ST11 a, the space within theprocessing vessel 12 is purged. To elaborate, the first gas G1 suppliedin the process ST11 a is exhausted. In the process ST12 a, an inert gassuch as a nitrogen gas may be supplied into the processing vessel 12 asa purge gas. That is, the purging in the process ST12 a may beimplemented by a gas purging of allowing the inert gas to flow in theprocessing vessel 12 or a purging by vacuum evacuation. In the processST12 a, surplus molecules adhering to the wafer W may be removed.Through the processes as stated above, the layer Ly1 of the reactionprecursor is formed to be a very thin monolayer.

In the process ST13 a following the process ST12 a, plasma P1 of asecond gas is generated within the processing vessel 12. To elaborate,the second gas containing a carbon dioxide gas is supplied into theprocessing vessel 12 from a gas source selected from the plurality ofgas sources belonging to the gas source group 40. The second gas may beanother gas containing oxygen atoms besides the carbon dioxide gas. Byway of non-limiting example, the second gas may be an oxygen gas. Thehigh frequency power is supplied from the first high frequency powersupply 62. At this time, the second high frequency power supply 64 mayalso apply the bias power. Further, it may be also possible to generatethe plasma by using only the second high frequency power supply 64without using the first high frequency power supply 62. By operating thegas exhaust device 50, the pressure of the space within the processingvessel 12 is set to a preset pressure.

The molecules (constituting the monolayer of the layer Ly1) adhering tothe surface of the wafer W through the process ST11 a as stated aboveincludes a bond between silicon and hydrogen. A binding energy of thesilicon and the hydrogen is lower than a binding energy of silicon andoxygen. Accordingly, as illustrated in FIG. 6B, if the plasma P1 of thesecond gas containing the carbon dioxide gas is generated, activespecies of the oxygen, for example, oxygen radicals are generated, andthe hydrogen of the molecules constituting the monolayer of the layerLy1 is substituted with oxygen, so that a layer Ly2 of silicon oxidefilm (for example, a SiO₂ film) is formed as a monolayer, as illustratedin FIG. 6C.

In the process ST14 a following the process ST13 a, the space within theprocessing vessel 12 is purged. To elaborate, the second gas supplied inthe process ST13 a is exhausted. In the process ST14 a, an inert gassuch as a nitrogen gas may be supplied into the processing vessel 12 asa purge gas. That is, the purging in the process ST14 a may beimplemented by the gas purging of allowing the inert gas to flow in theprocessing vessel 12 or the purging by vacuum evacuation.

In the above-described sequence SQ1 a, the purging is performed in theprocess ST12 a, and the hydrogen of the molecules constituting the layerLy1 is substituted with the oxygen in the process ST13 a following theprocess ST12 a. Accordingly, the same as in an ALD method, by performingthe single cycle of the sequence SQ1 a, the layer Ly2 of the siliconoxide film can be conformally formed on the main surface SC of the waferW in a thin uniform film thickness.

In the process ST15 a following the sequence SQ1 a, it is determinedwhether or not to finish the repetition of the sequence SQ1 a. Toelaborate, in the process ST15 a, it is determined whether therepetition number of the sequence SQ1 a has reached a preset number.Determining the repetition number of the sequence SQ1 a is determining afilm thickness TH of the protection film SX, which is the silicon oxidefilm, shown in FIG. 4A. That is, the thickness of the protection film SXfinally formed on the wafer W is determined by a product of the filmthickness of the silicon oxide film formed through a single cycle of thesequence SQ1 a and the repetition number of the sequence SQ1 a.Accordingly, the repetition number of the sequence SQ1 a is set based onthe required thickness of the protection film SX formed on the wafer W.

If it is determined in the process ST15 a that the repetition number ofthe sequence SQ1 a has not reached the preset number (process ST15 a:NO), the sequence SQ1 a is repeated. Meanwhile, if it is determined inthe process ST15 a that the repetition number of the sequence SQ1 a hasreached the preset number (process ST15 a: YES), the repetition of thesequence SQ1 a is finished. As a result, the protection film SX of thesilicon oxide film is formed on the main surface SC of the wafer W, asillustrated in FIG. 4A. That is, as the sequence SQ1 a is repeatedlyperformed the preset number of times, the protection film SX having thepreset film thickness is conformally formed on the main surface SC ofthe wafer W in the uniform thickness. The thickness of the protectionfilm SX is reduced as the repetition number of the sequence SQ1 a isdecreased.

Referring back to FIG. 1A to FIG. 1C, in the process ST2 following theprocess ST1, the bottom portion BT (surface SF2 b) of the groove portionTR is etched by plasma generated within the processing vessel 12. First,in the process ST2, a mixed gas of a third gas and a fourth gas issupplied into the processing vessel 12. The third gas may be aprocessing gas containing a fluorocarbon-based gas, and the fourth gasmay be a processing gas containing an oxygen gas. The third gas may be,by way of non-limiting example, a C₄F₈ gas. The fourth gas may be, byway of example, but not limitation, Ar/N₂/O₂. Plasma of the mixed gassupplied into the processing vessel 12 is generated within theprocessing vessel 12. To elaborate, a processing gas containing themixed gas of the third gas and the fourth gas is supplied into theprocessing vessel 12 from a gas source selected from the plurality ofgas sources belonging to the gas source group 40. The high frequencypower is supplied from the first high frequency power supply 62, and thehigh frequency bias power is supplied from the second high frequencypower supply 64. Further, by operating the gas exhaust device 50, theinternal pressure of the space within the processing vessel 12 is set toa preset pressure. As a result, the plasma of the mixed gas of the thirdgas and the fourth gas is generated. Active species of F (fluorine)contained in the plasma generated in the process ST2 etch the bottomportion BT of the groove portion TR of the etching target layer PM whichis the porous film. Subsequently, the space within the processing vessel12 is purged. To be specific, the processing gas supplied in the processST2 is exhausted from the inside of the processing vessel 12. An inertgas such as a nitrogen gas may be supplied into the processing vessel 12as a purge gas. That is, the purging performed in the process ST2 may bethe gas purging of allowing the inert gas to flow into the processingvessel 12 or the purging by vacuum evacuation.

As depicted in FIG. 4B, a depth of the groove portion TR is increased byperforming the single cycle of the sequence SQ1. Further, since theregion PM2 of the etching target layer PM at the protrusion portion CV2is etched from a side of the end surface SF3 through this single cycleof the sequence SQ1, a corner portion CP of the protrusion portion CV2is removed (chamfered) by this etching. That is, after the single cycleof the sequence SQ1 is conducted, there may be generated a height LP3 (aheight of the removed portion of the corner portion CP) between a tipend of the end surface SF3 of the region PM2 and an end surface of theprotection film SX provided on the surface SF2 c of the groove portionTR at the side of the protrusion portion CV2. The height LP3 that may begenerated in the method MT can be reduced by adjusting processingconditions such as a thickness of the protection film SX and an etchingtime. In the following description, the term “removed portion” refers toa portion removed by etching.

FIG. 7 is a diagram showing an example of a measurement result of acorrespondence between a film thickness TH of the protection film SXshown in FIG. 4A and the height LP3 of the corner portion CP after theetching shown in FIG. 4B. A vertical axis of FIG. 7 represents anincrement K (nm) of the removed portion of the corner portion CP (thatis, an increment of the height LP3) in the etching of 1 nm in theprocess ST2, and a horizontal axis of FIG. 7 indicates a value (nm) ofthe film thickness TH of the protection film SX provided on the surfaceSF2 c of the groove portion TR at the side of the protrusion portion CV2before the etching of the process ST2. A result GP1 is a measurementresult obtained when the high frequency bias power supplied from thesecond high frequency power supply 64 is 0 W; a result GP2, ameasurement result obtained when the high frequency bias power suppliedfrom the second high frequency power supply 64 is 25 W; and a resultGP3, a measurement result obtained when the high frequency bias powersupplied from the second high frequency power supply 64 is 100 W.

Referring to FIG. 7, the increment K of the removed portion of thecorner portion CP (that is, the increment of the height LP3) that hasoccurred in the etching of 1 nm in the process ST2 is found to increasewith a decrease of the film thickness TH of the protection film SXprovided on the surface SF2 c of the groove portion TR at the side ofthe protrusion portion CV2 and with an increase of the high frequencybias power supplied from the second high frequency power supply 64.Further, in case that a DC voltage is supplied from the power supply 70in the process ST2, the increment K of the removed portion of the cornerportion CP (that is, the increment of the height LP3) in the etching of1 nm is found to increase with a rise of the corresponding DC voltage.

Further, in any of the results GP1 to GP3, a variation of the incrementK of the removed portion of the corner portion CP (the increment of theheight LP3) with respect to a variation of the film thickness TH (thatis, an inclination of each graph of the results GP1 to GP3) is found tobe larger when the film thickness TH of the protection film SX is equalto or less than 2 nm as compared to a case when the film thickness TH ofthe protection film SX is larger than 2 nm. Accordingly, as can be seenfrom FIG. 7, if the film thickness TH of the protection film SX beforethe process ST2 is in the range form 2 nm to 8 nm, the removed portionof the corner portion CP caused in the etching of the process ST2 can bereduced, and the height LP3 of the removed portion of the corner portionCP can be reduced. Thus, degree of deformation of the etching targetlayer PM caused by the etching of the method MT can be reduced.

Now, the degree of anisotropy of the etching in the process ST2 will beexplained. Assuming that an etching rate in a vertical direction (adepth direction of the groove portion TR) is Y1 (nm/min) and an etchingrate in a horizontal direction (a direction which is perpendicular tothe vertical direction and in which the main surface SC of the wafer Wis expanded) is Y2 (nm/min), there is satisfied a relationship ofα=Y2/Y1, 0<α<1, which implies that the smaller the a is, the higher theanisotropy of the etching in the vertical direction may be. The value ais decreased with an increase of the high frequency bias power suppliedfrom the second high frequency power supply 64, and, also, is decreasedwith an increase of the internal pressure of the processing vessel 12.As stated, the degree of the anisotropy of the etching in the processST2 can be appropriately controlled by adjusting the high frequency biaspower supplied from the second high frequency power supply 64 and theinternal pressure of the processing vessel 12.

Now, referring to FIG. 1C, a case where the process ST1 b is used as theprocess ST1 shown in FIG. 1A will be explained. The process ST1 b is anexample of the process ST1 shown in FIG. 1A. The process ST1 b includesa process ST11 b and a process ST12 b. A processing detail of theprocess ST11 b is the same as the processing detail of the process ST11a. A processing detail of the process ST12 b is the same as theprocessing detail of the process ST12 a. That is, as depicted in FIG.4A, the protection film SX formed on the main surface SC of the wafer Wthrough the process ST1 b is the layer Ly1. Accordingly, in case thatthe process ST1 b is used as the process ST1, the film thickness of theprotection film SX formed through the single cycle of the sequence SQ1becomes equal to the film thickness of the protection film (layer Ly2)formed through the single cycle of the sequence SQ1 a.

In case that the process ST1 b is used as the process ST1, the formationof the layer Ly2 (see FIG. 6C) by the plasma P1 of the second gascontaining the oxygen atoms for use in the process ST13 a of the processST1 a may be implemented by the etching in the process ST2, asillustrated in FIG. 4B. That is, as the oxygen atoms contained in thefourth gas used in the process ST2 following the process ST1 b act thesame way as the oxygen atoms used in the process ST13 a of the processST1 a, the layer Ly2 is obtained from the layer Ly1. That is, the layerLy1 is formed through the process ST1 b, and the layer Ly2 is formedfrom the layer Ly1 by the etching of the process ST2 following theprocess ST1 b.

Reference is made back to FIG. 1A. In the method MT, the sequence SQ1 isperformed one or more times. In the process ST3 following the sequenceSQ1, it is determined whether or not to finish the repetition of thesequence SQL To elaborate, in the process ST3, it is determined whetherthe repetition number of the sequence SQ1 has reached a preset number.If it is determined in the process ST3 that the repetition number of thesequence SQ1 has not reached the preset number (process ST3: NO), thesequence SQ1 is repeated. Meanwhile, if it is determined in the processST3 that the repetition number of the sequence SQ1 has reached thepreset number (process ST3: YES), the repetition of the sequence SQ1 isfinished. As a result, the groove portion TR provided on the mainsurface SC of the wafer W can be formed to have a desired shape (desiredwidth and depth of the groove portion TR), as illustrated in FIG. 5B.FIG. 4A and FIG. 4B illustrate the states of the wafer W upon thecompletion of the first cycle of the sequence SQ1, whereas FIG. 5A andFIG. 5B illustrate the states of the wafer W upon the completion of thesecond cycle of the sequence SQL

The shape of the groove portion TR may be determined based on therepetition number of the sequence SQ1. That is, the width of the grooveportion TR (that is, the shape of the groove portion TR in a widthdirection) finally formed on the main surface SC of the wafer W issubstantially determined by a product of a film thickness of the siliconoxide film formed by the single cycle of the sequence SQ1 and therepetition number of the sequence SQ1. Further, the depth of the grooveportion TR (that is, the shape of the groove portion TR in the depthdirection) finally formed on the main surface SC of the wafer W issubstantially determined by a product of a depth of the groove portionTR etched by the single cycle of the sequence SQ1 and the repetitionnumber of the sequence SQ1. Thus, the repetition number of the sequenceSQ1 is set based on the required shape of the groove portion TR formedon the main surface SC of the wafer W.

Further, if the sequence SQ1 in which the process ST1 a of FIG. 1B isused as the process ST1 is included in multiple cycles of the sequenceSQ1 repeatedly performed, the detailed shape of the groove portion TRrelies on the repetition number of the sequence SQ1 a as well as therepetition number of the sequence SQL For example, in case that thesequence SQ1 is performed N times, there may be assumed a case where,among the N cycles of the sequence SQ1, the sequence SQ1 including theprocess ST1 a shown in FIG. 1B is performed M times (M is an integerequal to or larger than 1 and equal to or smaller than N−1) and thesequence SQ1 including the process ST1 b shown in FIG. 1C is performedN−M times. Particularly, there may be considered a case where, among theN cycles of the sequence SQ1, the sequence SQ1 including the process ST1a shown in FIG. 1B is first performed a single time, and then, in thesecond and subsequent cycles, the sequence SQ1 including the process ST1b shown in FIG. 1C is performed N−1 times. In this case, through thefirst cycle of the sequence SQ1, the protection film SX having arelatively thick film thickness TH can be first formed. If therepetition number of the sequence SQ1 including the process ST1 a isrelatively large, the etching target layer PM at the side of the surfaceSF2 of the groove portion TR may be altered by the plasma of the oxygengas used in the etching of the process ST13 a. Further, the depositionfilm DP may be removed by being etched by the plasma of this oxygen gas.In such a case, as the mask MK is exposed, the shape of the etchingtarget layer PM of the protrusion portion CV1 may be changed by thisetching.

Furthermore, referring to FIG. 5B, if the width of the groove portion TRis enlarged (the width LP1 of the groove portion TR is enlarged as thesurface SF2 a of the groove portion TR is enlarged in a direction DR1and the surface SF2 c of the groove portion TR is enlarged in adirection DR2) in the etching of the process ST2 due to the relativelylow anisotropy of the etching of the process ST2, the repetition numberN of the sequence SQ1 may be determined based on a required value dp ofthe depth LP4 of the groove portion TR and a required value lp of thewidth LP1 of the groove portion TR. Here, the required value dp of depthLP4 of the groove portion TR may be determined based on the value Y1(nm/min) of the etching rate in the vertical direction, a processingtime of each cycle of the sequence SQ1 and a value thy of the filmthickness TH of the protection film SX of each cycle of the sequenceSQ1. The required value lp of the width LP1 of the groove portion TR maybe determined based on the value Y2 (nm/min) of the etching rate in thehorizontal direction, the processing time of each cycle of the sequenceSQ1 and the value thy of the film thickness TH of the protection film SXof each cycle of the sequence SQL

Further, referring to FIG. 5B, if the width (width LP1) of the grooveportion TR is maintained in the etching of the process ST2 due to therelatively high anisotropy of the etching of the process ST2, therepetition number N of the sequence SQ1 may be determined by anexpression of N=(dp×tan(θ))/tha by using a required value tha (averagevalue) of the film thickness TH which can be formed through the singlecycle of the sequence SQ1, the required value dp of the depth LP4 of thegroove portion TR and a required shape of the groove portion TR(specifically, an angle θ shown in FIG. 5B). Here, the required valuetha (average value) of the film thickness TH that can be formed throughthe single cycle of the sequence SQ1 can be determined based on arequired value tht (maximum value) of the film thickness TH of theprotection film SX formed through the N cycles of the sequence SQ1 andthe repetition number N of the sequence SQ1 (tha=tht/N). The requiredvalue dp of the depth LP4 of the groove portion TR can be determinedbased on the value Y1 (nm/min) of the etching rate in the verticaldirection, the processing time of each cycle of the sequence SQ1 and thevalue thy of the film thickness TH of the protection film SX of eachcycle of the sequence SQ1. The angle θ shown in FIG. 5B can bedetermined based on the required value dp of the depth LP4 of the grooveportion TR and the required value tht of the film thickness TH of theprotection film SX (tan(θ)=tht/dp).

Below, examples of major processing conditions of the process ST2, theprocess ST11 a, the process ST13 a, the sequence SQ1 and the sequenceSQ1 a are specified.

<Process ST2>

-   -   Internal pressure (mTorr) of processing vessel 12: 80 mTorr    -   Value (W) of high frequency power of first high frequency power        supply 62 and value (MHz) of frequency: 300 W, 40 MHz    -   Value (W) of high frequency power of second high frequency power        supply 64 and value (MHz) of frequency: 25 W, 13 MHz    -   Value (V) of DC voltage of power supply 70: 0 V    -   Processing gas: C₄F₈/Ar/N₂/O₂ gas    -   Flow rate (sccm) of processing gas: C₄F₈ gas: 30 sccm, Ar gas:        1000 sccm, N₂ gas: 20 sccm, O₂ gas: 10 sccm    -   Processing time (s): 30 s

<Process ST11 a>

-   -   Internal pressure (mTorr) of processing vessel 12: 100 mTorr    -   Value (W) of high frequency power of first high frequency power        supply 62: 0 W    -   Value (W) of high frequency power of second high frequency power        supply 64: 0 W    -   Value (V) of DC voltage of power supply 70: 0 V    -   Processing gas (first gas): monoaminosilane (H₃—Si—R (R denotes        an amino group))    -   Flow rate (sccm) of processing gas: 50 sccm    -   Processing time (s): 15 s

<Process ST13 a>

-   -   Internal pressure (mTorr) of processing vessel 12: 200 mTorr    -   Value (W) of high frequency power of first high frequency power        supply 62: 300 W, 10 kHz, Duty 50    -   Value (W) of high frequency power of second high frequency power        supply 64: 0 W    -   Value (V) of DC voltage of power supply 70: 0 V    -   Processing gas (second gas): CO₂ gas    -   Flow rate (sccm) of processing gas: 300 sccm    -   Processing time (s): 5 s

<Sequence SQ1>

-   -   Repetition number: 5 times

<Sequence SQ1 a>

-   -   Repetition number 5 times

In the above-described method MT, the process ST1 of conformally formingthe protection film SX on the main surface SC of the wafer W (includingthe inner surface SF2 of the groove portion TR) and the process ST2 ofetching the bottom portion BT of the groove portion TR provided on themain surface SC after the process ST1 may be alternately repeated(process ST3). Thus, by appropriately adjusting the film thickness TH ofthe protection film SX or the like for each of the multiple cycles ofthe process ST1 and by appropriately adjusting the etching amount or thelike for each of the multiple cycles of the process ST2, the grooveportion TR can be processed with relatively high accuracy according tothe various required shapes of the groove portion TR.

Furthermore, in the process ST1 a, since the protection film SX isconformally formed on the main surface SC of the wafer W (including theinner surface SF2 of the groove portion TR) by the same method as theALD method, the strength of protection of the main surface SC of thewafer W can be improved, and the protection film SX for protecting themain surface SC of the wafer W can be formed in the uniform thickness.

Moreover, since the process ST1 b only consists of the process ST11 b offorming the reaction precursor (layer Ly1) on the main surface SC of thewafer W (including the inner surface SF2 of the groove portion TR) withthe first gas and the process ST12 b of purging the internal space ofthe processing vessel 12 after the completion of the process ST11 b, theprotection film SX formed through the process ST1 b can be formed of thereaction precursor (layer Ly1) formed in the process ST11 b, and,accordingly, can be a relatively thin film. In addition, since theplasma of the fourth gas containing oxygen is used in the process ST2following the process ST1 b, oxygen can be added to the reactionprecursor (layer Ly1) formed in the process ST11 b, and the protectionfilm SX having the same composition as the protection film formed by thesame method as the ALD method can be formed to have a relatively thinthickness. Furthermore, since the addition of the oxygen gas can beperformed during the etching of the process ST2, high efficiency of theprocessing can be achieved.

Further, in the process ST1 a, since the protection film SX isconformally formed on the main surface SC of the wafer W (including theinner surface SF2 of the groove portion TR) by the same method as theALD method, the strength of the protection of the main surface SC of thewafer W can be improved, and the protection film SX for protecting themain surface SC of the wafer W can be formed in the uniform thickness.Since the process ST1 b only consists of the process ST11 b of formingthe reaction precursor (layer Ly1) on the main surface SC of the wafer W(including the inner surface SF2 of the groove portion TR) with thefirst gas and the process ST12 b of purging the internal space of theprocessing vessel 12 after the completion of the process ST11 b, theprotection film SX formed through the process ST1 b can be formed of thereaction precursor (layer Ly1) formed in the process ST11 b, and,accordingly, can become a relatively thin film. In addition, since theplasma of the third gas containing oxygen is used in the process ST2following the process ST1 b, oxygen can be added to the reactionprecursor (layer Ly1) formed in the process ST11 b, and the protectionfilm SX having the same composition as the protection film formed by thesame method as the ALD method can be formed to have a relatively thinthickness. Furthermore, since the addition of the oxygen gas can beperformed during the etching of the process ST2, high efficiency of theprocessing can be achieved. Further, in performing the N cycles of thesequence SQ1, since the sequence SQ1 including the aforementionedprocess ST1 a is performed M times and the sequence SQ1 including theaforementioned process ST1 b is performed N−M times, it is possible tocope with the formation of various shapes of the groove portion TRsufficiently.

Further, since the second gas contains oxygen atoms, in the process ST13a, the reaction precursor (layer Ly1) of the silicon formed in theprocess ST11 a is bond with the oxygen atoms, so that the protectionfilm SX of the silicon oxide can be conformally formed. Moreover, incase that the second gas is a carbon dioxide gas, since the second gascontains the carbon atoms, damage caused by the oxygen atoms can besuppressed by the carbon atoms.

In addition, since the first gas contains the aminosilane-based gas, thereaction precursor (layer Ly1) of the silicon can be formed along anatomic layer of the main surface SC of the wafer W through the processST11 a and the process ST11 b.

Further, by using the first gas containing the monoaminosilane, thereaction precursor (layer Ly1) of the silicon can be formed through theprocess ST11 a and the process ST11 b.

Furthermore, aminosilane having one to three silicon atoms may be usedas the aminosilane-based gas contained in the first gas. Alternatively,aminosilane having one to three amino groups may be used as theaminosilane-based gas contained in the first gas.

Further, before the process ST2 is performed, if the film thickness THof the protection film SX formed in the process ST1 is in the range from2 nm to 8 nm, the etching effect upon the corner portion CP of the waferW covered with the protection film SX can be reduced, as compared to thecase where the film thickness TH of the protection film SX is below 2nm, particularly. Thus, the degree of deformation of the wafer W causedby the etching of the process ST2 can be reduced.

From the foregoing, it will be appreciated that the exemplary embodimentof the present disclosure has been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the embodiment disclosed herein is not intended to belimiting. The scope of the inventive concept is defined by the followingclaims and their equivalents rather than by the detailed description ofthe exemplary embodiment. It shall be understood that all modificationsand embodiments conceived from the meaning and scope of the claims andtheir equivalents are included in the scope of the inventive concept.

We claim:
 1. A method of processing a target object including a firstprotrusion portion, a second protrusion portion, an etching target layerand a groove portion, the etching target layer having a region belongingto the first protrusion portion and a region belonging to the secondprotrusion portion, the groove portion being provided on a main surfaceof the target object, being provided on the etching target layer andbeing defined by the first protrusion portion and the second protrusionportion, and an inner surface of the groove portion being included inthe main surface of the target object, the method comprising: performinga first sequence repeatedly N times (N is an integer equal to or largerthan 2), wherein the first sequence comprises: forming a protection filmconformally on the main surface of the target object in a processingvessel of a plasma processing apparatus in which the target object isaccommodated; and etching a bottom portion of the groove portion of thetarget object with plasma of a gas generated within the processingvessel after the forming of the protection film conformally isperformed.
 2. The method of claim 1, wherein, in the forming of theprotection film conformally, the protection film is conformally formedon the main surface of the target object by repeatedly performing asecond sequence comprising; supplying a first gas into the processingvessel; purging a space within the processing vessel after the supplyingof the first gas is performed; generating plasma of a second gas withinthe processing vessel after the purging of the space is performed; andpurging the space within the processing vessel after the generating ofthe plasma of the second gas is performed, wherein, in the supplying ofthe first gas, plasma of the first gas is not generated.
 3. The methodof claim 1, wherein, in the forming of the protection film conformally,the protection film is conformally formed on the main surface of thetarget object by supplying a first gas into the processing vessel andpurging a space within the processing vessel after the supplying of thefirst gas is performed, in the etching of the bottom portion of thegroove portion, the bottom portion of the groove portion of the targetobject is etched with plasma of an oxygen-containing gas generatedwithin the processing vessel, and in the supplying of the first gas,plasma of the first gas is not generated.
 4. The method of claim 1,wherein, in the performing of the first sequence repeatedly N times, thefirst sequence including a first processing is performed M times (M isan integer equal to or lager than 1 and equal to or smaller than N−1),and the first sequence including a second processing is performed N−Mtimes, wherein the first processing is included in the forming of theprotection film conformally, in the first processing, the protectionfilm is conformally formed on the main surface of the target object byrepeatedly performing a second sequence comprising: supplying a firstgas into the processing vessel; purging a space within the processingvessel after the supplying of the first gas is performed; generatingplasma of a second gas within the processing vessel after the purging ofthe space is performed; and purging the space within the processingvessel after the generating of the plasma of the second gas isperformed, wherein the second processing is included in the forming ofthe protection film conformally, in the second processing, theprotection film is conformally formed on the main surface of the targetobject by supplying the first gas into the processing vessel and purgingthe space within the processing vessel after the supplying of the firstgas is performed, in the etching of the bottom portion of the grooveportion following the second processing, the bottom portion of thegroove portion of the target object is etched by plasma of anoxygen-containing gas generated within the processing vessel, and plasmaof the first gas is not generated in the supplying of the first gasperformed in the first processing and the supplying of the first gasperformed in the second processing.
 5. The method of claim 2, whereinthe second gas contains oxygen atoms.
 6. The method of claim 5, whereinthe second gas contains a carbon dioxide gas or an oxygen gas.
 7. Themethod of claim 2, wherein the first gas contains an aminosilane-basedgas.
 8. The method of claim 7, wherein the first gas containsmonoaminosilane.
 9. The method of claim 7, wherein the aminosilane-basedgas contained in the first gas includes aminosilane having one to threesilicon atoms.
 10. The method of claim 7, wherein the aminosilane-basedgas contained in the first gas includes aminosilane having one to threeamino groups.
 11. The method of claim 1, wherein a film thickness of theprotection film formed in the forming of the protection film conformallyis equal to or larger than 2 nm and equal to or smaller than 8 nm beforethe etching of the bottom portion of the groove portion is performed.